The present disclosure is generally related to toner processes, and more specifically, to aggregation and coalescence processes for the preparation of toner compositions wherein a complexing or sequestering agent is added during the aggregation process.
Provided are toner processes for the economical chemical in situ preparation of toners without the utilization of the known pulverization and/or classification methods, and wherein in embodiments toner compositions with a volume average diameter of about 1 to about 25 and more specifically about 1 to about 10 microns, and a narrow geometric size distribution (GSD) of, for example, about 1.14 to about 1.25 as measured on the Coulter Counter, can be obtained. The resulting toners can be selected for known electrophotographic imaging, digital, printing processes, including color processes, and lithography.
In reprographic technologies, such as xerographic and ionographic devices, toners with volume average diameter particle sizes of form about 9 microns to about 20 microns are effectively utilized. Moreover, in xerographic technologies, such as the high volume Xerox Corporation 5090 copier duplicator, high resolution characteristics and low image noise are highly desired, and can be attained utilizing the small sized toners as disclosed herein having, for example, a volume average particle diameter of from about 2 to about 11 microns, or less than about 7 microns, and with a narrow geometric size distribution (GSD) of from about 1.14 to about 1.25 or about 1.16 to about 1.20. Additionally, in xerographic systems wherein process color is utilized, such as pictorial color applications, small particle size colored toners, for example from about 3 to about 9 microns, are desired to avoid paper curling. Also, small toner particle sizes can be selected, such as from about 1 to about 7 microns, and with higher colorant loading, such as from about 5 to about 12 percent by weight of toner, such that the mass of toner layers deposited onto the substrate such as paper is reduced to obtain the same quality of image and resulting in a thinner plastic toner layer on paper after fusing, thereby minimizing or avoiding paper curling.
Toners prepared in accordance with the present disclosure provide desired fusing characteristics including, for example, desired release characteristics such as stripping force, for example of less than about 30 grams of force to less than about 5 grams of force, desired blocking characteristics such as for example, a high blocking temperature of about 45° C. to about 65° C., desired document offset characteristics, such as a document offset of about 2.0 to about 5.0 desired vinyl offset characteristics, such as a vinyl offset of about 3.0 to about 5.0 and desired triboelectrical charging characteristics. Further, toners prepared in accordance with the present disclosure enable in embodiments, the use of lower minimum imaging fusing temperatures, such as from about 120° C. to about 170° C., enable high speed printing such as for machines running at greater than about 35 pages per minute. Further, the present toner processes and toners enable high image gloss, such as in an oil-less fuser system while still retaining a high blocking temperature, high image gloss comprising for example from about 30 to about 60 gloss units (GGU) as measured by the Gardner Gloss metering unit, a high image gloss of greater than about 30 GGU, greater than about 40 GGU, or greater than about 50 GGU, for example on a coated paper, such as Xerox 120 gsm Digital Coated Gloss papers.
Numerous processes are known for the preparation of toners, such as, for example, conventional polyester processes wherein a resin is melt kneaded or extruded with a pigment, micronized and pulverized to provide toner particles with a volume average particle diameter of from about 9 microns to about 20 microns and with broad geometric size distribution of from about 1.26 to about 1.5. In these processes, it is usually necessary to subject the aforementioned toners to a classification procedure such that the geometric size distribution of from about 1.2 to about 1.4 is attained. Also, in the aforementioned conventional processes, low toner yields after classifications may be obtained. Generally, during the preparation of toners with average particle size diameters of from about 11 microns to about 15 microns, toner yields range from about 70 percent to about 85 percent after classification. Additionally, during the preparation of smaller sized toners with particle sizes of from abut 7 microns to about 11 microns, lower toner yields can be obtained after classification, such as from about 50 percent to about 70 percent. With the present processes, small average particle sizes of, for example, from about 3 microns to about 9 microns, and more specifically, about 4 to about 6 microns or about 5 microns, are attained without resorting to classification processes, and wherein narrow geometric size distributions are attained, such as from about 1.14 to about 1.30, or from about 1.14 to about 1.25. High toner yields are also attained such as from about 90 percent to about 98 percent. In addition, by the present toner processes, small particle size toners of from about 3 microns to about 7 microns can be economically prepared in high yields such as from about 90 percent to about 98 percent by weight based on the weight of all of the toner ingredients, such as toner resin and colorant.
In U.S. Pat. No. 6,132,924, the disclosure of which is totally incorporated herein by reference, there is illustrated a process for the preparation of toner comprising mixing a colorant a latex, and a coagulant, followed by aggregation and coalescence, wherein the coagulant may be a polyaluminum chloride.
In U.S. Pat. No. 6,268,102, the disclosure of which is totally incorporated herein by reference, there is illustrated a process for the preparation of toner comprising mixing a colorant, a latex, and a coagulant, followed by aggregation and coalescence, wherein the coagulant may be a polyaluminum sulfosilicate.
Illustrated in U.S. Pat. No. 5,994,020, the disclosure of which is totally incorporated herein by reference, are toner preparation processes, and more specifically, a process for the preparation of toner comprising: (i) preparing, or providing a colorant dispersion; (ii) preparing, or providing a functionalized wax dispersion comprised of a functionalized wax contained in a dispersant mixture comprised of a nonionic surfactant, an ionic surfactant, or mixtures thereof; (iii) shearing the resulting mixture of the functionalized wax dispersion (ii) and the colorant dispersion (i) with a latex or emulsion blend comprised of resin contained in a mixture of an anionic surfactant and a nonionic surfactant; (iv) heating the resulting sheared blend of (iii) below about the glass transition temperature (Tg) of the resin particles; (v) optionally adding additional anionic surfactant to the resulting aggregated suspension of (iv) to prevent, or minimize additional particle growth of the resulting electrostatically bound toner size aggregates during coalescence (iv);heating the resulting mixture of (v) above about the Tg of the resin; and optionally, (vii) separating the toner particles.
With respect to the references, only a small part thereof has been selected and this part may or may not be fully representative of the prior art teachings or disclosures.
Emulsion/aggregation/coalescence processes for the preparation of toners are illustrated in a number of Xerox patents, the disclosures of each of which are totally incorporated herein by reference, such as U.S. Pat. No. 5,290,654, U.S. Pat. No. 5,278,020, U.S. Pat. No. 5,308,734, U.S. Pat. No. 5,370,963, U.S. Pat. No. 5,344,738, U.S. Pat. No. 5,403,693, U.S. Pat. No. 5,418,108, U.S. Pat. No. 5,364,729, and U.S. Pat. No. 5,346,797; and also of interest may be U.S. Pat. Nos. 5,348,832; 5,405,728; 5,366,841; 5,496,676; 5,527,658; 5,585,215; 5,650,255; 5,650,256; 5,501,935; 5,723,253; 5,744,520; 5,763,133; 5,766,818; 5,747,215; 5,827,633; 5,853,944; 5,804,349; 5,840,462; 5,869,215; 5,863,698; 5,902,710; 5,910,387; 5,916,725; 5,919,595; 5,925,488; 5,977,210; 5,994,020; 6,020,101; 6,130,021; 6,120,967 and 6,628,102.
In addition, the following U.S. patents relate to emulsion aggregation processes of forming toner compositions, the disclosures of each of which are totally incorporated herein by reference.
U.S. Pat. No. 5,922,501 describes a process for the preparation of toner comprising blending an aqueous colorant dispersion and a latex resin emulsion, and which latex resin is generated from a dimeric acrylic acid, an oligomer acrylic acid, or mixtures thereof and a monomer; heating the resulting mixture at a temperature about equal, or below about the glass transition temperature (Tg) of the latex resin to form aggregates; heating the resulting aggregates at a temperature about equal to, or above about the Tg of the latex resin to effect coalescence and fusing of the aggregates; and optionally isolating the toner product, washing, and drying.
U.S. Pat. No. 5,945,245 describes a surfactant free process for the preparation of toner comprising heating a mixture of an emulsion latex, a colorant, and an organic complexing agent.
U.S. Pat. No. 5,482,812 describes a process for the preparation of toner compositions or toner particles comprising (i) providing an aqueous pigment dispersion comprised of a pigment, an ionic surfactant, and optionally a charge control agent; (ii) providing a wax dispersion comprised of, wax, a dispersant comprised of nonionic surfactant, ionic surfactant or mixtures thereof; (iii) shearing a mixture of the wax dispersion and the pigment dispersion with a latex or emulsion blend comprised of resin, a counterionic surfactant with a charge polarity of opposite sign to that of said ionic surfactant, and a nonionic surfactant; (iv) heating the above sheared blend below about the glass transition temperature (Tg) of the resin to form electrostatically bound toner size aggregates with a narrow particle size distribution; (v) adding additional ionic surfactant to the aggregated suspension of (iv) to ensure that no, or minimal additional particle growth of the electrostatically bound toner size aggregates occurs on further increasing the temperature to coalesce the aggregates into toner particles (vi); (vi) heating the mixture of (v) with bound aggregates above about or at the Tg of the resin; and optionally (vii) separating the toner particles from the aqueous slurry by filtration and thereafter optionally washing.
U.S. Pat. No. 5,622,806 describes a process, for example, for the preparation of toner compositions with controlled particle size comprising (i) preparing a pigment dispersion in water, which dispersion is comprised of a pigment, an ionic surfactant in amounts of from about 0.5 to about 10 percent by weight to water, and an optional charge control agent; (ii) shearing the pigment dispersion with a latex mixture comprised of a counterionic surfactant with a charge polarity of opposite sign to that of the ionic surfactant, a nonionic surfactant, and resin particles, thereby causing a flocculation or heterocoagulation of the formed particles of pigment, resin, and charge control agent; and (iii) stirring.
The appropriate components and process aspects of the each of the foregoing U.S. Patents may be selected for the present disclosure in embodiments thereof